Lady Jane Grey ( – ), also known as Lady Jane Dudley[1] or The Nine Days' Queen, was an English noblewoman and de facto monarch of England from 10 July until 19 July 1553.

The great-granddaughter of Henry VII through his younger daughter Mary, Jane was a first cousin once removed of Edward VI. In May 1553, she was married to Lord Guildford Dudley, a younger son of Edward's chief minister, John Dudley, Duke of Northumberland. When the 15-year-old King lay dying in June 1553, he nominated Jane as successor to the Crown in his will, thus subverting the claims of his half-sisters Mary and Elizabeth under the Third Succession Act. Jane was imprisoned in the Tower of London when the Privy Council decided to change sides and proclaim Mary as queen on 19 July 1553. Jane was convicted of high treason in November 1553, which carried a sentence of death, although her life was initially spared. Wyatt's rebellion of January and February 1554 against Queen Mary I's plans for a Spanish match led to the execution of Jane, at the age of 16 or 17, and also of her husband.

Lady Jane Grey had an excellent humanist education and a reputation as one of the most learned young women of her day. A committed Protestant, she was posthumously regarded as not only a political victim but also a martyr.